Sarah Brown
Orchid mushrooms are not a variety of mushroom but are instead tiny mushrooms that sometimes grow in orchid pots. Orchid seeds are very small and spindle-shaped, and they lack the necessary nutritional support to grow on their own. Instead, they rely on fungal symbionts in natural habitats to provide the nutrients needed for germination. The reliance of orchids on specific fungi has been widely studied, and the presence of certain fungi in the soil has proved to be of greater importance in seed germination than the orchid's proximity to older plants or their geographical location. Orchid mushrooms are therefore a sign of a healthy orchid.
| Characteristics | Values |
|---|---|
| Orchid seeds | Very small (0.35mm to 1.50mm long), spindle-shaped, and have an opening at the pointed end |
| Orchid seed embryo | Undifferentiated and lacks root and shoot meristems |
| Orchid seed nutrition | Lacks endosperm and relies on fungal symbionts in natural habitats for germination |
| Orchid germination | Forms an intermediate structure called protocorm, which consists mainly of parenchyma cells |
| Orchid root system | Small amount of thick unbranched roots, resulting in a small surface area favorable for potentially mycotrophic tissue |
| Orchid mycorrhiza | Defined by the formation of pelotons in root cortical cells, which are intracellular hyphal coils produced by the fungus |
| Peloton size and arrangement | Varies in size, density, and arrangement of hyphae |
| Peloton separation | Maintained by an interfacial matrix and the orchid's plasma membrane |
| Orchid cells with degenerating pelotons | Lack starch grains |
| Orchid cells with newly invaded pelotons | Contain large starch grains, suggesting hydrolysis of starch resulting from fungal colonization |
| Effect of fungal colonization | Enlargement of the nucleus in infected orchid cortical cells and nearby non-infected cortical cells |
| Fungi that form orchid mycorrhizae | Typically basidiomycetes |
| Orchid myco-heterotrophy | Orchids that cannot photosynthesize derive all their nutritional needs from fungal networks |
| Orchid-fungal relationship | Orchids tap into the mycelial network and obtain carbon and nutrients needed for survival and reproduction |
| Orchid seed germination | Likely only occurs when infected with specific fungi |
| Orchid potting mix | May contain mushroom spores, requiring a full replant to remove |
| Orchid care | Avoid fertilizers with nitrogen, which promotes fungal growth |
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What You'll Learn
- Orchid mushrooms are harmless fungi that feed on decaying tissue
- Orchid seeds are very small and lack the ability to grow on their own
- Orchids rely on fungal symbionts for germination and development
- Orchid mycorrhiza is characterised by the formation of pelotons in root cortical cells
- Orchids without chlorophyll depend on fungi for their entire lives
Orchid mushrooms are harmless fungi that feed on decaying tissue
Orchid mushrooms can appear in orchid pots due to the presence of mushroom spores in the potting mix, roots, or pot. If the presence of mushrooms is bothersome, it is recommended to replant the orchid in a new substrate to remove any spores. However, this may not be necessary, as orchid mushrooms are generally harmless to the plant.
The relationship between orchids and fungi is quite complex. Orchids rely on specific fungi for germination and development into protocorms, which are young plants that have germinated but lack leaves. Orchid seeds are small and lack the necessary nutritional support to grow on their own, so they depend on fungal symbionts in their natural habitats to provide the nutrients needed for germination. The presence of certain fungi in the soil has been shown to be more important for seed germination than the orchid's proximity to older plants or its geographical location.
Fungi can enter an orchid at various life stages, including the seed, protocorm, late-staged seedling, or adult plant root. Once the fungus enters the orchid, it produces intracellular hyphal coils called pelotons in the embryos of developing seedlings and the roots of adult plants. Orchid mycorrhiza, a specific type of fungus-orchid relationship, is characterised by the formation of these pelotons, which can vary in size and arrangement. The interaction between the orchid and the fungus can lead to physiological and structural changes, such as the enlargement of the nucleus in infected orchid cortical cells.
Some orchids, such as Dipodium atropurpureum, are myco-heterotrophic, meaning they derive all their nutritional needs from fungal networks. These orchids lack chlorophyll and rely on the fungus for carbon. The fungal networks collect micronutrients from the soil and carbon from nearby trees, and the orchids tap into this network to obtain the resources they need to survive and reproduce.
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Orchid seeds are very small and lack the ability to grow on their own
Orchid seeds are very small, typically ranging from 0.35mm to 1.50mm in length, and have a unique spindle shape with an opening at the pointed end. Their diminutive size, however, is not their only distinguishing feature. Orchid seeds also stand out due to their inability to grow independently, a trait that sets them apart from the seeds of many other plants.
This lack of self-sufficiency in germination is due to the absence of essential nutrients within the seeds themselves. Unlike many other types of seeds, orchid seeds do not contain endosperm, which is a nutrient-rich tissue that supports the growth and development of an embryo. As a result of this deficiency, orchid seeds must rely on external sources of nutrition to initiate and sustain their growth.
The solution to this challenge lies in the symbiotic relationship orchids have evolved with specific fungi. In their natural habitats, orchid seeds obtain the necessary nutrients for germination from these fungal symbionts. This reliance on fungi is so profound that even after germination, young orchid plants, known as protocorms, continue to benefit from the presence of these fungal partners. The fungi enhance the vigour of the protocorms and contribute to their metabolic capacity.
The fungi that play this crucial role in the life cycle of orchids are typically basidiomycetes. They form a unique structure called pelotons, which are intracellular hyphal coils that develop within the embryos and roots of orchids. The formation of pelotons is a defining feature of orchid mycorrhiza, a specialised type of symbiotic relationship between orchids and fungi. This relationship is so strong that some orchids retain their fungal symbionts throughout their entire lives, remaining dependent on the fungus for carbon and other essential nutrients.
While the specific mechanisms and complexities of this relationship are still being studied and understood, it is clear that orchid seeds, despite their tiny size, have evolved a remarkable strategy for survival by harnessing the support of fungal partners. This interdependence between orchids and fungi showcases the intricate and fascinating ways in which different organisms collaborate and influence each other in the natural world.
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Orchids rely on fungal symbionts for germination and development
Orchid seeds lack endosperms and contain very limited storage reserves. Orchid germination and development into protocorms are reliant upon fungal symbionts, which decrease the time of germination and increase the vigour of the protocorm. Orchid seeds form an intermediate structure called protocorms, which are young plants that have germinated but lack leaves and consist mainly of parenchyma cells. In the earliest stages, orchids rely entirely on their mycorrhizal fungi for all nutrients, including carbon. Mycorrhizas play an important role in plant growth and development. Fungi supply soil mineral nutrients, such as nitrogen and phosphorus, to their host plants in exchange for carbon resources. Plants gain as much as 80% of their mineral nutrient requirements from mycorrhizal fungi, which form associations with the roots of over 90% of all plant species.
The symbiosis with mycorrhizal fungi is essential for orchid seed germination and protocorm development under natural conditions. Epiphytic orchids grow on other plants and may produce chlorophyll in their leaves, stems, and roots. Terrestrial orchids have been found to commonly associate with Tulasnellaceae, however, some autotrophic and non-autotrophic orchids do associate with several ectomycorrhizal fungi. Epiphytic fungi may associate more commonly with limited clades of rhizoctonia, a polyphyletic grouping. These fungi may form significant symbioses with either an epiphytic or terrestrial orchid, but rarely do they associate with both. Orchid mycorrhizas have been widely studied, and the populations of certain fungi present in the soil have proved to be of greater importance in seed germination than the orchid's proximity to older plants or their geographical location.
The knowledge of species-specific fungal symbionts is crucial given the endangered status of many orchids. The identification of their fungal symbionts could prove useful in the preservation and reintroduction of threatened orchids. Researchers in India have used samples from adult orchids to germinate seeds from an endangered orchid, which were found to associate closely with Ceratobasidium. The debate over whether fungal symbiosis is necessary for the orchid is an old one, as Noël Bernard first proposed orchid symbiosis in 1899. In 1922, the American botanist Lewis Knudson discovered that orchid seeds could be grown on agar and fungal sugars without mycorrhizae, however, modern research has found that the germination of orchids may be more successful with specific fungi.
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Orchid mycorrhiza is characterised by the formation of pelotons in root cortical cells
Orchid mushrooms are not actual mushrooms but fungi that grow on decaying wood and other organic particles. They are harmless to orchids and are simply the fruiting body of the fungus, which is largely composed of mycelium (filaments).
Orchid mycorrhiza is a type of symbiotic relationship between orchids and fungi. It is characterised by the formation of pelotons in the root cortical cells of the orchid. This structure differentiates orchid mycorrhiza from other forms of fungi. Pelotons are coiled, dense fungal hyphae that facilitate nutrient exchange between the fungus and the orchid. They are surrounded by the orchid's plasma membrane, which invaginates to accommodate the growing pelotons. The interfacial matrix that separates the pelotons from the orchid's cytoplasm is composed of material that varies depending on the stage of interaction between the fungus and the orchid.
The pelotons range in size and the arrangement and density of their hyphae. As pelotons age, they disintegrate and appear as brown or yellow clumps in the orchid cells. This disintegration is an area of interest in current research, as new pelotons continue to form, indicating high hyphal activity. The collapse of pelotons may be a result of the host plant's defence mechanism against uncontrolled fungal development.
The formation of pelotons in orchid mycorrhiza involves significant genetic upregulation and downregulation to facilitate symbiosis and nutrient transfer. The primary amino acid synthesised and transferred is arginine, which is catabolised into ammonium and transported into the plant cell. Orchid mycorrhiza provides the orchid with nutrients, especially sugars and water, and plays a crucial role in seed germination and seedling establishment.
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Orchids without chlorophyll depend on fungi for their entire lives
Orchid mushrooms are tiny mushrooms that sometimes grow in orchid pots. They are saprophytes, meaning they feed on decaying tissue. Orchid mushrooms are not harmful to the orchid and can simply be cut off if they are bothersome. Orchid mushrooms are not to be confused with orchid fungi, which are essential to the growth of orchids.
Some orchids lack chlorophyll and are called achlorophyllous mycoheterotrophs. These orchids rely on fungi for their entire lives, depending on the fungus for nutrients, sugars, minerals, and carbon. Orchid seeds germinate and develop into protocorms with the help of fungal symbionts, which decrease the time of germination and increase the vigor of the protocorm. Orchid mycorrhizal interactions encompass a large variety of symbiotic scenarios, ranging from fully mycoheterotrophic plants that are parasitic on their fungal inhabitants, such as Monotropa uniflora, to bidirectional nutrient transport interactions, such as in green-leaved Goodyera repens.
The symbiosis between orchids and fungi was first proposed by Noël Bernard in 1899. In 1922, American botanist Lewis Knudson discovered that orchid seeds could be grown on agar and fungal sugars without mycorrhizae. However, modern research has found that the germination of orchids may be more successful with specific types of fungi. Orchid cells with degenerating pelotons, which are intracellular hyphal coils produced by the fungus, lack starch grains, while newly invaded orchid cells contain large starch grains, suggesting the hydrolysis of starch resulting from fungal colonization.
The reliance of orchids on specific fungi has been widely studied, and the presence of certain fungi in the soil has been found to impact orchid populations. Orchid mycorrhizal interactions involve the transfer of nitrogen, phosphorus, and carbon from the fungus to the orchid. This transfer occurs through live pelotons, but it has also been observed that large amounts of carbon and nitrogen may be taken up by the orchid during the senescence and digestion of fungal pelotons in a process called mycophagy. The lysis of pelotons begins between 30 and 40 hours after contact, and the presence of certain organelles indicates their role in digesting fungal cells.
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Frequently asked questions
Orchid mushrooms are mushrooms that grow in orchid pots or are otherwise associated with orchids. Orchid seeds are very small and spindle-shaped and rely on fungal symbionts in natural habitats to provide the nutrients needed for germination.
The mushrooms are harmless and live on decaying wood and other organic particles. You can cut them off if you want, but they are just the fruiting body of the fungus, so they will likely grow back. If you want to get rid of them, you can repot your orchid in a fresh potting mix after sterilizing the plant and the pot.
Orchids rely on specific fungi for germination and development. The populations of certain fungi present in the soil have been proven to be of greater importance in seed germination than the orchid's proximity to older plants or their geographical location.
